docstr: Broadcasts the tensor to all parties.
docstr_tok: ["Broadcasts","the","tensor","to","all","parties","."]
code: def broadcast(self, tensor, src, async_op=False):
      """Broadcasts the tensor to all parties."""
      if async_op:
          raise NotImplementedError()
  
      if self.rank == src:
          for i in range(self.get_world_size()):
              self.mailbox[i].put(tensor.clone())
  
      # No need for a barrier here.
  
      return self.mailbox[self.rank].get()
  
imports: import logging
  import threading
  from operator import itemgetter
  from queue import Queue
  import torch
  from torch.distributed import ReduceOp
  from .communicator import Communicator
label_desc: Use image node_id 16 for calling the InProcessCommunicator obj's underlying member method code with example usage: obj.broadcast(tensor, src, async_op) and returns: self